In the past, the color of a product produced by an extrusion device has been monitored and controlled in an off-line manner. Typically, the extrusion device or system would be operated until color equilibrium was achieved, followed by collection of a product having a certain color. The spool of collected product would then be removed from the system, and taken to a color laboratory where the color would be measured using an off-line spectrometer. Then, once a color evaluation was made, the spool would be returned to the extrusion device or system, adjustments would be made to the level of the colorant provided to the extrusion device, and another run of about ten minutes or so would be commenced. This process would be repeated until evaluation of the color of the product in the color laboratory indicated that the desired color, within acceptable limits, had been achieved.
The latter process was not only time-consuming and inefficient, but also resulted in substantial waste. That is to say, a large amount of scrap material was produced and wasted during each run. Thus, if several runs during a given period of time were necessary in order to evaluate and adjust the color of the product, a very substantial amount of waste material would result.
The latter system or process was also inefficient from the standpoint of time in that each run would take about ten minutes or so, and then the color evaluation in the laboratory would take another thirty minutes to one hour. Thus, if several repetitions of the evaluation process were necessary before the final acceptable coloration was achieved, the entire pre-production process could take several hours.
Accordingly, there has been a need for the development of an on-line color monitoring and control system and method. Moreover, there is a need for the development of such an on-line color monitoring and control system and method employing the most modern optical technology for both transmission of incident light toward the product and reflection of light from the product, as well as handling and transfer of the light through an optical spectrum analyzer to that portion of the system which actually performs the evaluation of the coloration of the product.
It is recognized that on-line measurement of the color of extruded pellets in compounding operations is known in the art. For example, see the following: U.S. Pat. No. 3,972,854--Costolow and U.S. Pat. No. 5,559,173--Campo. In addition, on-line color control of fiber extrusion has been achieved by measuring the color of a fiber melt. In this regard, see U.S. Pat. No. 4,684,488--Rudolph.
Nevertheless, measurement of the color of moving yarn or fiber (or a filament of a yarn), or of a collection of fibers, is not known in the prior art. Moreover, the employment of alternative sensor mechanisms for measuring color of an extruded product prior to spooling and on-spool, respectively, is also not known in the art. Finally, employment of means for quickly checking the color measurement signal against a reference signal, and specifically use of an optical switch to accomplish that purpose, are also not known in the art.
Therefore, there is a need in the art for development of an on-line color monitoring and control system and method which measures the color of moving yarn or fiber (or filament of a yarn), or of a collection of fibers. Mechanisms for measurement of color both prior to spooling and on-spool are also needed. Finally, a means for quickly checking the color measurement signal against a reference signal, using an optical switch, is also needed.
The following patents are considered to be of background interest relative to the present invention, and are burdened by the disadvantages of prior art methods and arrangements, as discussed above: U.S. Pat. No. 5,526,285--Campo et al.; U.S. Pat. No. 5,468,586--Proper et al.; U.S. Pat. No. 5,387,381--Saloom; U.S. Pat. No. 5,282,141--Faas et al.; U.S. Pat. No. 5,092,168--Baker; U.S. Pat. No. 5,053,176--Cameron et al.; U.S. Pat. No. 4,788,650--Willis et al.; U.S. Pat. No. 4,761,129--Aste et al.; U.S. Pat. No. 4,745,555--Connelly et al.; U.S. Pat. No. 4,688,178--Connelly et al.; U.S. Pat. No. 3,388,261--Roberts et al.;